264 EDWARD S. MORSE. 



The manner of burrowing is peculiar. In one case an indi- 

 vidual buried itself siphon end downward, and for three days 

 remained in this position with its disk-like foot level with the 

 surface of the mud. In every case the individual rested on the 

 bottom of the dish, ventral region uppermost and valves widely 

 open, limited only by the closed portion of the mantle which is 

 drawn tense by the distended valves. When placed on the 

 surface of sand or mud it soon pushes itself backward by means 

 of its foot which, assuming a pointed tongue-like shape, is thrust 

 forward and downward lifting the anterior end and thus depress- 

 ing the posterior end. Others buried themselves and went to 

 the bottom of the dish, where they remained in a horizontal 

 position. Whether they went head first or tail first was not 

 observed. Others buried themselves in the mud and remained 

 out of sight for hours with no burrows communicating with the 

 surface. Drew states that Nucula delphinodonta buries itself in 

 the mud with no surface communication. The strong alternate 

 movements of the sides of the siphonal area may be related to 

 the habit of burying itself posterior end downward. As a further 

 proof that Solcnomya buries itself siphon end downward may be 

 cited the condition of a young Solenomya borealis preserved in 

 alcohol for dissection. I found adhering to the anterior end of 

 the shell close to the margin three colonies of a 'species of sponge. 

 Here was an evidence that the creature had not only been 

 buried siphon end downward, but that the anterior end had 

 been slightly protruded above the level of the sand and had 

 remained in that position long enough for the accumulation of 

 foreign growth. The periosteum is so exceedingly smooth and 

 polished, and the creature is so active in its swimming habits 

 that the adhesion of foreign growth would hardly be looked for. 1 

 An examination of a number of shells show r ed little evidence of 

 wear or burial at either end. The pedal opening is so large and 

 the activities of the foot are so incessant that more water is 

 admitted anteriorly than posteriorly and the siphonal opening 

 has little to do so far as conveying water and food to the gill 

 cavity is concerned. 



1 Dr. Drew inform? me that in digging this species from the mud many of them 

 float on the surface of the water, the periosteum repelling the water as if oiled. 



